Scientists at Purdue University have developed a portable generator that uses trash as its primary fuel source.

Called a tactical biorefinery, the device was designed at the behest of the U.S. Army. But researchers say the generators could also be used in civilian situations, such as emergencies that require portable generators.

About the size of a small moving van, the diesel generator can process several types of refuse, including paper, plastic, Styrofoam, cardboard, woodchips and food waste.

"This is a very promising technology," Michael Ladisch, a Purdue professor of agricultural and biological engineering who leads the project, said Thursday in a statement. "In a very short time, it should be ready for use in the military, and I think it could be used outside the military."

The biorefinery uses two different processes to create fuel.

The machine separates food material into a bioreactor that uses the yeast ferments to create ethanol.

Other materials go to a gasifier and are converted into propane gas and methane, which then fuel the diesel engine that creates electricity.

The system is designed to run on diesel oil for several hours until the gasifier and the bioreactor begin to produce fuel, researchers said.

The Army commissioned completion of a prototype and is considering it for future use. According to its builders, the system lowers the potential danger and expense of transporting fuel and waste and helps cover the tracks of mobile military units because it destroys trash--the evidence of their presence.

The generator is also an environmentally friendly alternative to traditional diesel generators, they say. Using biomass as a fuel is less polluting than oil because plants absorb carbon dioxide, according to scientists at Indiana-based Purdue.

Also, they note that the system is efficient, with the first prototype producing about 90 percent more energy than it consumes.